1. Field of the Invention
The present invention relates to signal amplification, and switching power modulation and control.
2. Description of the Related Art
It is known for an electronic circuit for producing an output voltage and current to a load to include a controller and multiple high current semiconductor switches. Further, if output voltages are desired to be of greater magnitude than the supply voltage may allow, a boost power converter may be used. The power converter may include one or more power inductors, with two controlled switches arranged to operate in a boost switch configuration. The controller may, based on parameters associated with applied input signal levels, and based on the load impedance, apply boost power in order to transfer more electrical energy from an input source of the power converter to the load in accordance with the requirement to recreate a sufficiently larger replica of the input signal.
A problem with common digital audio amplifier switching audio power output stages is that they can be electrically noisy because the most common Class A-D amplifier configuration delivers a significant amount of the switching carrier wave to the output terminals, especially at no-signal conditions. Class B-D amplification is better because no-signal transitions do not deliver current to the load, but rail-to-rail common mode transitions still radiate and burn power in the output filters. This causes energy loss as radio frequency noise and/or heat as well as added cost in filter components to suppress the radio frequency noise.
A further problem with similarly capable high-power boost mode switching power amplifiers is the need to optimize efficiency. Boost power supplies in these configurations can be required to track the amplifier voltage requirements for best efficiency related to output level. Lower amplifier supply voltages are preferred when smaller signals are applied to reduce power loss. This requires a means to control the voltage boost based on input signal amplitude while the DC-DC regulator provides a low output impedance to the amplifier to prevent unwanted switching ripple that may be presented to the output. This usually requires use of a shunt capacitor. This capacitor creates a further dilemma because it needs to be big enough to prevent power supply noise but small enough to move fast enough to stay up with and replicate large audio transients. To solve this problem, further complexity is needed to add an analog-to-digital converter and digital delay to the input signal path along with a level detector, and a control signal to enable the boost supply when needed.
Another common concern with two switch boost power systems is that these designs cannot reduce the amplifier supply voltage below the supply input voltage. Newer designs solve this problem by integrating buck capability with at least two more switches in the regulator architecture and can further improve performance by eliminating the slowing regulator output capacitor and employing a comprehensive cycle-by-cycle analysis in order to determine what operating mode will be employed next to best match the needs of precision current delivery. This design approach has resulted in a proliferation of extensive digital signal processing complexity as well as redundant power device use in order to get a plurality of possible selected operating modes to link to the converter and output stage in a manner that achieves delivery of high power and wide dynamic range.